Originally Posted By: wagga
According to this sailing terms xlation site, knot = knoop, and nautical mile is zeemijl.

And according to babelfish, Dutch to English, knoop = button. I suppose actual tied knots might have been used as button-like fasteners way back when the language was evolving.

And for the origin of knots being used as a nautical unit of speed, read this:
    Chip Log on Wikipedia   ...interesting.